Furnace

ABSTRACT

A furnace, in particular for an electro thermal atomization device of an atom absorption spectrometer, has a heatable heat duct in which is mounted a trial platform. The trial platform is essentially basin-shaped with radially inward-turned rims, at least at its free ends.  
     In order to make ongoing improvements in a furnace of the aforementioned type, so that the trial platform has an increased lifetime along with high reproducibility of measurements and simple operation as well as low cost, the trial platform features a geometric structure stabilization device which reduces the ratio of effective volume of the trial platform to the rim volume.

[0001] This invention claims priority of pending German PatentApplication 101 28 272.9 filed on Jun. 12, 2001.

FIELD OF THE INVENTION

[0002] The invention relates to a furnace, in particular for an electrothermal atomization device of an atom absorption spectrometer, with aheatable heat duct in which is mounted a trial platform, which isessentially basin-shaped with radially inward-turned rims, at least atits free ends.

BACKGROUND OF THE INVENTION

[0003] A trial atomization is performed on the trial platform. After theappropriate supply of heat within the heat duct, through the irradiationof electromagnetic waves of determined frequency into the heat ductthese waves are absorbed by the atomized trial and a resultingabsorption spectrum is registered, which is characteristic for therespective trial. The corresponding absorption spectrum is determined bythe atom absorption spectrometer.

[0004] The trial platform has a certain effective volume, into which thecorresponding trial can be inserted by means of a pipette or the like.At its free ends, the basically basin-shaped trial platform is generallyequipped with partially circular rims, which restrict the effectivevolume in a lateral direction.

[0005] Trial platforms in common use heretofore have proved, atrelatively high temperatures and especially under the impact of stronglyoxidizing reagents, to lose their shape and to give way against aninside wall of the heat duct. This increases the contact surface betweenthe trial platform and the heat duct, resulting in such a strong heatingof the trial platform by the introduction of heat from the heat ductthat there is no longer an optimal temperature delay relative to theheat duct. Such a temperature delay, however, is desirable in order toimprove and stabilize the atomization conditions for the elements to bedetermined, also in respect to continuing high increments of heat athigh temperature.

[0006] It should also be mentioned that, even with a minor loss of shapeof the trial platform, the measurements are no longer reproducible. Forall these reasons the trial platform must be replaced if there is acorresponding loss of shape. This is relatively difficult and, in somecases, in addition to the trial platform the heat duct at least mustalso be replaced, resulting in increased costs.

[0007] The invention therefore aims to make ongoing improvements in afurnace of the aforementioned type, so that the trial platform has anincreased lifetime along with high reproducibility of measurements andsimple operation as well as low costs.

[0008] In conjunction with the characteristics of the first patentclaim, this task is fulfilled in that the trial platform has a geometricstructure stabilization device, which reduces the ratio of the effectivevolume of the trial platform to the rim volume.

[0009] The structure stabilization device prevents the trial platformfrom prematurely losing its shape and keeps the contact surfaces betweenthe trial platform and the heat duct from increasing. As a result, onthe one hand, the lifetime of the trial platform is increased. Anincreased lifetime also leads to a cost reduction in operating thefurnace. In addition, the stabilized structure of the trial platformresults in a good reproducibility of the measurements carried out withthe trial platform. Another result of the stabilized structure is thateven aggressive media can be injected into it better and with increasedlifetime of the trial platform and can be measured by means of an atomicabsorption spectrometer.

[0010] It is true that the effective volume of the trial platform is tosome extent reduced by the structure stabilization device. Thisreduction, however, is relatively slight, so that sufficient trialmaterial can be injected even with the inventive trial platform. Inaddition, the trial platform of this invention can be larger than aknown trial platform while retaining the same amount of space in theheat duct, and thus the effective volumes of the inventive trialplatform and of the known trial platform are essentially equal.

[0011] The inventive trial platform can be used particularly in a heatedgraphite atomizer (HGA). This is also true for transversally heatedgraphite atomizers (THGA).

[0012] To ensure that the trial platform is easy to operate and that itcan fit in the heat duct, it can be integrated into the heat duct. Theintegration is normally ensured by means of a basically punctiformconnection with the heat duct. In the remaining area no direct contactshould exist between the trial platform and the heat duct, in order tominimize any heating through the addition of heat between the tube andthe platform.

[0013] Such an integrated trial platform is generally of small mass andhas a relatively large surface. In the case of one trial platform incommon use, its length for example is 10 mm, the thickness of the rim is0.47 mm, and the corresponding height of the rim is 0.08 mm. Because ofthe small mass and the great surface, the trial platform can be heatedup quickly by heat rays emitted from the heat duct. The punctiformconnection with the heat duct results in an optimal temperature delaywith respect to the tube, a very desirable characteristic for a trialplatform with stabilized temperature.

[0014] A trial platform that can be produced simply and relativelyeconomically, which contains little uncleanliness, and which isrelatively easy to operate can be formed of graphite as its basematerial. A surface coating is generally applied to this base materialpyrolytically. The surface coating increases the chemical stability ofthe platform.

[0015] In order to maintain the known advantages of existing trialplatforms in the inventive trial platform without having to use othermaterials, additional materials, additional structural elements or thelike, the invention proposes the geometrical structure stabilizationdevice. This installation can, for instance, be configured through areduction of the platform length. The corresponding length reduction incomparison to the existing trial platforms results, in simple manner, ina stabilization of the trial platform, considerably prolonging itseffective life; that is, the shape of the trial platform is stable for alonger period.

[0016] Such a length reduction and other minor modifications in thegeometry of the trial platform can lead to a smaller effective volume.This is tolerable, however, since the effective volume of the inventivetrial platform remains well suited for receiving a sufficient trialquantity for carrying out corresponding measurements.

[0017] It was observed that the platform length could be reduced by 10to 40 percent in comparison to known platforms while maintaining asufficiently large effective volume. It is considered advantageous tohave a reduction between 15 and 35 percent, and especially favorable ifit is in the range of 20 to 30 percent. A 30 percent reduction in lengthwill result, for instance, from a decrease in platform length from 10 mmto 7 mm.

[0018] Another means of forming the structure stabilization device,while maintaining the length of the trial platform, is by increasing therim thickness of the platform. Otherwise the other geometric dimensionsof the trial platform can be maintained unchanged in comparison to aknown trial platform.

[0019] Even a great rim thickness results in a low decrease in theeffective volume which in no way affects the use of the trial platformfor conducting corresponding measurements.

[0020] It was observed that increases in the rim thickness ranging from10 to 50 percent in comparison to known platforms are sufficient. Athickening of 25 to 45 percent is preferable, and a thickening of 30 to40 percent is particularly advantageous. An increase in rim thickness of0.65 mm produces a thickening of the rim by about 38 percent, forinstance, in comparison to a rim thickness of 0.47 mm in a known trialplatform.

[0021] An additional means of configuring the geometric structurestabilization device is through an increase in the height of the rim.Once again the other geometric dimensions of the trial platform canremain unchanged in comparison to known trial platforms. In increasingthe height of the rim, care must be taken that it is not so great as toinfluence the irradiated electromagnetic waves that are to be absorbedby the atomized trial. This can occur, for instance, through a moreprecise arrangement of the heat duct and/or trial platform relative tothe direction of radiation of the electromagnetic waves.

[0022] It has been shown that it is possible to increase the rim heightof the trial platform by 40 to 240 percent in comparison to known trialplatforms. An increase of 80 to 200 percent is preferable, and of 100 to150 percent is particularly advantageous. For instance, a 125 percentincrease of rim height has been achieved with a rim height of 0.18 mm asopposed to a rim height of 0.08 mm in a trial platform that is in commonuse.

[0023] In relation to the aforementioned concrete values, it should bepointed out that they are provided only by way of example. Acorresponding geometric structure stabilization device can also be usedin trial platforms in current use, which have other concrete values forlength, rim thickness, and rim height.

[0024] In order to stabilize the inventive structure still further, thegeometric structure stabilization device can simultaneously include areduction of the platform length and/or an increase of the rim thicknessand/or an increase of the rim height.

[0025] Since the trial platform as a rule always includes a certainpretensioning, there can be an additional advantageous impact on thispretensioning if an increase in rim thickness and/or in the rim heightis arranged, for instance, at just one end of the platform. In thisrespect, it is important to remember that it is possible, for instance,that an increase in rim thickness could occur at one end of he platformand an increase in rim height at the other end, or vice versa.

[0026] It is possible, in addition, that an increase in both rimthickness and rim height could occur at one end, whereas at the otherend of the platform there is only an increase in rim height or in rimthickness. Other combinations of corresponding geometric structurestabilization devices are obvious.

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In the following discussion, advantageous embodiments of theinvention will be examined in greater detail with the help of theassociated illustrations. The illustrations are as follows.

[0028]FIG. 1 A perspective top view of an exploded furnace with heatduct.

[0029]FIG. 2 A partially cut-out detailed view of an element of FIG. 1.

[0030]FIG. 3 An initial model of a trial platform in the heat ductaccording to FIG. 2, in a partially cut-out view.

[0031]FIG. 4 A second model of a trial platform in a view comparable tothat of FIG. 3.

[0032]FIG. 5 A third model of a trial platform in a view comparable tothat of FIG. 3.

DETAILED DESCRIPTION OF THE DRAWINGS

[0033]FIG. 1 depicts an inventive furnace 1 consisting of three furnaceparts 12, 13, and 14, in a perspective top view. The middle oven part 14contains a heat duct 2 in which, as seen in FIG. 2, a trial platform 3is integrated. A trial can be conducted to this platform by way of atrial opening 15 on an upper side of the middle oven part 14 by means ofa pipette or the like.

[0034] The heat duct 2 includes two cylindrical extensions of mediumcaliber, to which a right or left furnace part 12, 13 can be attached.In particular, the heat duct 2 is warmed by means of the bored holes.

[0035] The left furnace part 13 has a housing 18 into which the middlefurnace part 14 can be installed. If this middle furnace part isattached in the housing 18, the trial opening 15 is aligned with theopening 19 and the ends of the heat duct 2 are aligned with the openings20 in the housing 18.

[0036]FIG. 2 shows the middle furnace part 14 in isolated position andpartly cut out. In particular, the arrangement of the trial platform 3can be recognized inside the heat duct 2.

[0037]FIG. 3 presents an initial model of a trial platform 3 with ageometric structure stabilization device 8. The corresponding heat duct2 is partly cut away and in the interior of the heat duct the basicallybasin-shaped trial platform 3 is approximately centered on thelongitudinal axis of the heat duct 2. The trial platform has a rim 6, 7on its ends 4, 5. This rim has the shape of a circle segment and standsradially inward from the trial platform 3.

[0038] In the model shown in FIG. 3, the geometric structurestabilization device 8 is formed by an increase of at least rimthickness 10 of the rim 5. On the other hand, the rim 6 has an unchangedrim thickness 16. An effective volume of the trial platform 3 is formedbetween the rims 6, 7 and by the corresponding rim height. Thiseffective volume can be filled by way of the trial opening with acorresponding trial.

[0039] The rim 6 can also be formed with an increased rim thickness 10corresponding to rim 5. In this case the geometric structurestabilization device 8 would be formed by the increased rim thickness 10of both rims 6, 7.

[0040]FIG. 4 depicts a second model for a trial platform 3. Thisembodiment is distinguished from the one in FIG. 3 by the fact that therim 7 on the end 5 of the trial platform 3 has an increased rim height11 in comparison with the rim height of rim 6. Analogously to FIG. 3,this increased rim height 11 can also be provided for rim 6 at the otherend 4 of the trial platform 3.

[0041] In the model in FIG. 4, the geometric structure stabilizationdevice 8 is formed by the increased rim height 11.

[0042] In connection with the model according to FIGS. 3 and 4, itshould be mentioned that a platform length 9 as in FIG. 5 is unchangedand is equal in both models. In addition, the models in FIGS. 3 and 4can be combined, since for instance rim 7 has both the increased rimthickness 10 and the increased rim height 11. Finally, it is alsopossible that, for instance in the model of FIG. 4, the rim 6 on the end4 of the trial platform 3 is provided with an increased rim thickness 10as in FIG. 3, or the rim 6 of FIG. 3 is equipped with an increased rimheight 11 as in FIG. 4.

[0043] A third model of a trial platform is shown in FIG. 3. This modelis differentiated from the preceding models by the fact that theplatform length 9 is reduced in comparison to the platform length 17while maintaining the thickness and heights of the rims 6, 7. Thecorresponding geometric structure stabilization device 8 is formed bythis reduction of the platform length 9.

[0044] It should be mentioned that also in this connection it ispossible to combine the various models of FIGS. 3 to 5. An example ofsuch a combination occurs if the trial platform 3, with reduced platformlength 9 for instance, has an increased rim thickness 10 and/or anincreased rim height 11 on one or both rims 6, 7. Analogously, in themodels of FIGS. 3 and 4 as well, the platform length can be reduced tocorrespond to FIG. 5.

[0045] As a result of the invention, through a simple geometricstructure stabilization device a trial platform of a heat duct isfurther improved in its ability to retain its shape by the fact that thelifetime of the trial platform is considerably increased; that is, acontact between trial platform and heat duct is reduced to theessentially punctiform connection between them, while otherwise thetrial platform and heat duct are arranged at a distance from oneanother. Thanks to this improved shape retention of the trial platform,remarkable advantages can be achieved with simple means while retainingall advantages of known trial platforms in current use. In addition tothe increased stable shape in itself, there is also a long-termstability even at high temperatures inside the furnace. Thereproducibility of measurements conducted by the inventive trialplatforms is extremely high and is also ensured over a lengthy period oftime.

[0046] At the same time, the proposed geometric structure stabilizationdevices in no way influence the structure of the trial platform or thematerials used for the trial platform, since no additional structuralelements or additional materials need to be used.

In the claims:
 1. Furnace (1), in particular for a geometric structurestabilization device of an atom absorption spectrometer, with a heatableheat duct (2) inside which there is mounted a trial platform (3), whichis essentially basin-shaped with radially inward-turned rims, at leastat its free ends (4, 5), characterized in that the trial platform (3)has a geometric structure stabilization device (8) that reduces theratio of effective volume of the trial platform to the rim volume. 2.Furnace in accordance with claim 1, characterized in that the furnace(1) is a heated graphite atomizer that, in particular, is transversallyheatable.
 3. Furnace in accordance with claim 1, characterized in thatthe trial platform (3) is integrated in the heat duct (2).
 4. Furnace inaccordance with one of the foregoing claims, characterized in that thetrial platform (3) is formed of graphite as base material, on which anovercoating is applied pyrolytically.
 5. Furnace in accordance with oneof the foregoing claims, characterized in that the geometric structurestabilization device (8) is formed by a reduction of the platform length(9).
 6. Furnace in accordance with claim 5, characterized in that thereduction of the platform length (9) is in the range from 10 to 40percent, preferably 15 to 35 percent, and most advantageously between 20and 35 percent.
 7. Furnace in accordance with one of the foregoingclaims, characterized in that the geometric structure stabilizationdevice (8) is formed by an increase in the rim thickness (10). 8.Furnace in accordance with claim 7, characterized in that the increasein rim thickness is in the range between 10 and 50 percent, preferablybetween 25 and 45 percent, and most advantageously between 30 and 40percent.
 9. Furnace in accordance with one of the foregoing claims,characterized in that the geometric structure stabilization device (8)is formed by an increase in the rim height (11) of the trial platform(3).
 10. Furnace in accordance with claim 9, characterized in that theincrease in the rim height is in the range between 40 and 250 percent,preferably between 80 and 200 percent, and most advantageously between100 and 150 percent.
 11. Furnace in accordance with one of the foregoingclaims, characterized in that the geometric structure stabilizationdevice (8) simultaneously includes a reduction of the platform length(9) and/or an increase in the rim thickness and/or an increase in therim height (11).
 12. Furnace in accordance with one of the foregoingclaims, characterized in that the increase in the rim thickness (10)and/or the increase in the rim height (11) is found at least on one end(4, 5) of the trial platform (3).